The present invention relates to culvert structures and more particularly to low headroom culvert structures fabricated from shallow arch shaped flat or non-corrugated sections and girder-like beams made up of upstanding reinforcing rib elements disposed on the outside of the culvert. The instant invention is especially useful in the construction of hydraulic culverts. A "hydraulic culvert" as used in the instant specification and claims is intended to mean a drain structure used primarily to carry off high volumes and high velocity flows of water or the like caused by runoff, flooding, cloudbursts, etc.
In the past shallow arch low headroom culverts were normally fabricated from heavy guage metal sections and they sometimes required reinforcing concrete sections and/or reinforcing metal ribs. In other instances they were made from specially configured matching metal plate elements secured together by various complex fixtures and/or fasteners. Examples of such prior art culvert sections are to be found in U.S. Pat. Nos. 538,432; 587,392; 625,795; 800,953; 832,017; 905,290; 950,928; 1,013,440; 1,040,442; 1,926,843; 1,935,273; 1,999,500; 2,343,029; 4,141,666; 4,318,635; and 4,459,063 as well as the culvert structures described and discussed in various copyrighted brochures of Kaiser Aluminum & Chemical Corporation or Kaiser Aluminum & Chemical Sales, Inc., such as "Aluminum Box Culvert" Copyrighted in 1983, "Aluminum Structural Plate" Copyrighted in 1974 and 1985, "Aluminum Storm Sewers" Copyrighted in 1976, and "Aluminum Storm Water Control" Copyrighted in 1983. Other approaches to improving hydraulic capacity and flow are represented by the smooth walled metal spiral culverts of U.S. Pat. Nos. 4,161,811; 4,161,194; and 3,487,537.
The culverts of U.S. Pat. No. 4,141,666 and the aforesaid brochure entitled "Aluminum Box Culvert" are of particular interest. The low headroom culverts of these references were built from corrugated metal sheet or plate in order to meet the stringent and rigid strength requirements of the regulatory bodies and standard setting commissions of the various states and/or counties in the states. Corrugated sheet and plate sections, however, have various disadvantages. For example, they pose problems in corrugation matching at the joints because of the manufacturing pitch and depth tolerances of the matching corrugations. This results not only in an increase in installation time and effort but in fabrication costs because of the need to develop special tools to treat the end portions of the corrugations so they will mate and properly interfit. Corrugated sections also require more metal than flattened sections to cover the same surface areas and this increase in metal costs is passed on to the customer user. Last but not least corrugated culvert sections are not always truly efficient in carrying off water because of the inherent surface roughness of the sections due to the corrugations. This in turn means that for a given cross-sectional area of corrugated culvert the total volume of fluid, e.g., water, carried by the culvert in a given time period will be much less than in the case where the walls of the culvert are smooth. In short the corrugations retard water flow and the deeper the corrugations the more restricted the flow.
The net result is that such prior art corrugated metal wall culverts were not always the most efficient drainage mediums particularly in the case of hydraulic culverts designed particularly to carry high volumes of water and high velocity water runoff. By avoiding the use of corrugated sections and internal strengthening elements that project into the culvert the non-corrugated culvert of the instant invention by virtue of its novel construction can still retain satisfactory drainage characteristics while using less material, etc. The instant culvert structure relies substantially entirely on the girder-like arched cross beams provided by improved cross ribbing elements as the primary load bearing members in the culvert. The relatively high bending moment continuity of each beam is maintained from one side edge of the culvert to the other by virtue of the improved construction of the beams and their attachment to the metal sheeting. Further advantageous features of the instant invention will be observed by reference to the following detailed description when taken in conjunction with the appending drawings.